Biomimetic multilayer small-diameter vascular grafts with tunable mechanical behavior

Small-diameter vascular grafts remain limited by thrombosis, intimal hyperplasia, and inadequate mechanical and biological integration, motivating manufacturing strategies that can simultaneously control tubular architecture, mechanical response, and the blood-contacting interface. Herein, we report a bioinspired coaxial dry-jet wet-spinning platform using a custom-engineered three-channel spinneret to continuously fabricate bilayer thermoplastic polyurethane/polylactic acid (TPU/PLA) hollow constructs with an external TPU layer, a luminal PLA layer, and a sacrificial water core. Rheological screening identified compatible TPU/PLA processing windows, while systematic variation of polymer and bore-fluid injection rates enabled regulation of wall geometry and axial mechanical properties. The higher-solids 18T22P formulation consistently exhibited greater tensile and dynamic stiffness than 14T18P, and the construct fabricated at 1.0 mL min^-1 provided a balanced response with an ultimate tensile strength of 5.84 ± 0.69 MPa, Young's modulus of 171.51 ± 23.85 MPa, and storage modulus of 190.36 MPa at 37 °C. Following 14 days of PBS conditioning, mass loss remained below 1%, although tensile-strength and modulus retention decreased to approximately 51% and 55%, respectively. Plasma activation followed by type I collagen coating increased surface wettability, with a 4 h coating condition maximizing NIH/3T3 attachment. The collagen-functionalized PLA lumen supported enhanced HUVEC attachment and maintained short-term endothelial metabolic activity comparable to a collagen control. Both polymer interfaces exhibited negligible hemolytic responses, comparable platelet adhesion, and delayed whole-blood clot development relative to the blank condition. Collectively, this work establishes a process-structure-property-biointerface framework for continuously manufactured multilayer hollow constructs with tunable mechanics and favorable preliminary vascular-cell and blood compatibility.